Novel approaches beyond standard immunofluorescence for kidney biopsies

Abstract

Purpose of reviewImmunofluorescence on frozen tissue (IF-F) utilizing antibodies against immunoglobulin (Ig) heavy and light chains (IgA, IgG and IgM, kappa and lambda) and components of classical and alternative complement pathways (C1q, C3c and C4) is the standard of renal pathology. However, conventional IF-F has limitations, particularly in nephropathies associated with organized and/or monoclonal Ig deposits. This review will discuss new applications of established methods beyond conventional IF-F and recent novel immunohistochemical methods. Recent findingsThe combined application of paraffin immunofluorescence (IF-P) and IgG subtype staining excluded monotypic deposits in 62--66% of DNA J homolog subfamily B member 9-associated fibrillary glomerulonephritis (FGN) with apparent monotypic deposits by IF-F, whereas IF-P unmasks IgG deposits in a subset of cases of immunotactoid glomerulopathy. A novel IF technique targeting epitopes at the junction of the Ig heavy and light chains was introduced and unmasked polytypic deposits in a subset of glomerulonephritis with apparent monotypic deposits on IF-F. A recent study described the successful application of co-detection by indexing (CODEX) multiplexed IF to visualize more than a dozen target antigens within a single kidney tissue section. Finally, immunohistochemical protocols for detection of the novel antigens in membranous nephropathy have already entered the clinical practice of renal pathology. SummaryNovel ancillary techniques in renal pathology have the potential to significantly enhance our ability to evaluate renal biopsies.

IgM kappa proliferative glomerulonephritis with monoclonal immunoglobulin deposition complicated with nocardiosis dermatitis: a case report and review of literature

“…Moreover, according to previous studies, the determination of Ig deposition with the IF-F method may yield false negative result, which is termed "masked deposits, " and the reason for this issue is related to the destruction of antigens in frozen sections (21)(22)(23). Paraffin immunofluorescence (IF-P) is a valuable salvage technique, as antigen retrieval in IF-P staining can unmask immune deposits; thus, IF-P is more sensitive than IF-F in some renal diseases such as PGNMID (24). Recent studies show that RF IgM has different affinities.…”

Systemic vasculitis involving the kidney: the nephropathologist’s point of view

“…In approximately 30% of the cases vasculitic lesions are described with vascular PAS-positive deposits, endoluminal accumulation of lymphocytes and fibrinoid necrotizing changes in more advanced stages of the disease 47 . Findings in IF may reflect the composition of the cryoglobulins depending on the clinical type, with IgG and/or IgM showing smudgy and coarsely granular positivity of different intensity, with co-deposition of C3 and polytypic or monotypic (most frequently kappa) light chains 48 . Electron microscopy reveals peculiar electron dense deposits located mainly in mesangial, subendothelial and intracapillary spaces, with characteristic substructure organisation in 12-20 nm randomly arranged and non-branching fibrils alternated with 20-35 nm microtubules 49 .…”